Electric switching system



Dec. 4, 1951 H, REX 7 2,577,155

ELECTRIC SWITCHING SYSTEM Filed Feb. 23, 1946 um/zn r/o/v CIRCUIT 1.

InVenTor' Charles H- Rexb g Patented Dec. 4, 1951 ELECTRIC SWITCHING SYSTEM Charles H. Rex, Marblehead, Mass., assignor to General Electric Company, a corporation of New York Application February 23, 1946, Serial No. 649,593

8 Claims. 1

My invention relates to electric switching systems, and more particularly to holding circuits for electromagnetic switching means arranged for energization through a program switch which is recurrently opened and closed during a desired holding interval. The invention is especially applicable to program selector drums of the type wherein adjustable camming pins are so arranged that the cooperating program cam switch will not be held actuated as it passes between pins in adjacent positions.

It is a general object of my invention to provide new and improved program means for controlling an electromagnetic switching system.

It is a further object of my invention to provide new and improved circuit holding means operable in conjunction with a program switch of the type which is recurrently opened and closed during a desired holding interval.

It is a particular object of my invention to provide a new and improved switching system for a program selector of the type including a program switch which is actuated for only a portion of any of a plurality of selectable unit time intervals, as by adjustable pins in a revolving drum.

In accordance with my invention, an electromagnetic switch or contactor provided with holding or locking means is energized through the recurrently actuated program switch. The energizing current, however, is not made or broken at the program switch, but at a timing switch which is closed for only a portion of each closing interval of the program switch. Further means are provided for disabling the holding or locking means during only an initial or included portion of each closing interval of the timing switch. Thus, in those positions of the program selector in which the program switch is actuated, the contactor energizing circuit is completed and the holding means simultaneously disabled; but the holding means is again rendered operable before the energizing circuit is broken. On the other hand, in those positions of the selector where he program switch is not actuated, the energizing circuit is never completed, but the holding eans is disabled at least momentarily.

My invention will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing, in which Figs. 1 and 2 are schematic circuit diagrams of electromagnetic program switching systems illustrating various embodiments of my invention.

Referring first to Fig. 1, I have illustrated diagrammatically a rotatable program drum I driven by a motor 2 and provided with a plurality of adjustable switch actuating pins 3. The pins 3 may, for example, be selectably positioned in any of a plurality of holes around the entire periphery of the drum I. The camming pins 3 cooperate with a program switch comprising a stationary contact 4 and a movable contact 5 mounted upon a resilient spring strip 6. The spring strip 6 is fixedly mounted at one end and is provided at its other end with a turned-down camming extension i arranged to engage the pins 3 in the drum i.

The camming pins 3 are so formed that, even when positioned in adjacent holes in the drum I, each pin causes a separate actuation of the program switch 6. Thus, where a plurality of pins 3 are arranged in adjacent holes of the drum to define a desired continuous holding interval, the program switch 6 is recurrently actuated to close its contacts a plurality of times during the holding interval.

In order to overcome the effect of recurrent actuation of the program switch 6 during a single holding interval, the switch 6 is arranged to energize an electromagnetic contactor 8 which is provided with holding means independent of the drum I. The contactor 8 comprises a normally open switch contact 9 arranged to connect a desired utilization circuit Hi to a suitable source of electric current supply indicated by the symbol 13+. An energizing winding H for the contactor 8 is arranged to be connected to the supply source B+ through the program switch contacts 4, 5 in series circuit relation with the contacts of a normally open timing switch I2. The contacts of the timing switch I2 are periodically closed by a cam I3 driven by a timing motor I l. The cam I3 is arranged to make one complete revolution in the unit time interval defined by the time required for the drum I to revolve through the angular distance between two adjacent holes or pins in its periphery.

The contactor 8 of Fig. 1 is of the self-latching type, and includes a latching detent I5 arranged for cooperation with a spring biased latch I 6. Electromagnetic means including a coil I! are provided for releasing the latch I6. The release coil IT is arranged to be energized from the supply source B+ through a normally open timing switch I8. The contacts of the timing switch I8 are periodically closed at least momentarily at the same frequency as the switch I2 by a cam I9 driven by the timing motor I4.

In operation, the program drum I and the timing cams I3 and I9 are continuously rotated at difierent speeds. The drum I defines a continuous series of unit time intervals equal in length to the time taken for the drum l to rotate the angular distance between adjacent pins or holes in its periphery. The cams l3 and I9 each make one complete revolution in each such unit time interval. By way of example, let it be assumed that the unit time intervals defined by the distance between adjacent holes in the drum 1 are of twelve minutes duration, so that the cams i3 and is make one complete revolution each twelve minutes.

The cam I3 is provided with a shoulder 20 arranged to close the contacts ofthe switch [2 for a predetermined period during each unit time interval. Similarly, the cam i9 is provided with a shoulder 2! arranged to close the contacts of the switch 18 at least momentarily during an initial portion of each closing period of theswitch 12. By way of example, let it be assumed that the shoulder 28 closes the switch l2 for thirty seconds during each twelve minutes, and that the shoulder 28 closes the switch it for the first twenty seconds or" each thirty-second closure periodoi the switch (2.

It is to be noted also that the closure periods of the switch i2 are arranged to fall in those portions or" the twelve-minute intervals defined by the drum during which the'program switch 5 is directly over a hole in the drum or is closed by a pin if a pin is positioned in that hole.

Let it now be assumed that the first of a group of adjacent pins comes under the program switch 6 and closes the switch. Then, during the closing interval of the contacts c and 5, the timing switch it will be closed for thirty seconds. Thus, an energizing circuit will be completed for the contactor coil ii and the contactor 8 picked up. During the first twenty seconds of this energizing interval, the latch i5 is rendered ineffective by the closure of the timing switch l8. However, before the timing switch I2 is opened, the timing switch it! is opened, so that when the switch 52 is finally opened at the end of the thirty seconds, the contactor S is retained in its energized position by the latch it.

If new, during the next twelve-ninute interval defined by the drum l, the program switch 6 encounters another pin the same simultaneous energization and sequential deenergization of the closing coil 5 l and the release coil l'l will take place, with the closing coil taking precedence because it is the last to be deenergized. Thus, the contactcr 8 will be held in its energized position for a total holding interval defined by the number of adjacent pins in the drum I. When the last pin or" group passes the program switch 5 so that, upon the next closure of the timing switch 2, the program contacts 4 and 5 remain .open, the contactor closing coil l i will not be energized, but the release coil I! will be energized through the timing switch It. Thus, at the first opportunity after the passage of the last pin of a series, the contactor & will be dropped out and will remain out until the program switch 6 encounters another pin on the drum.

t will be evident that the arrangement of Fig. 1 may be modified for use with a contactor having a holding coil in place of the release coil iii. For such use, it is only necessary to arrange the timing switch it to beinormally closed and periodically opened, rather than normally open and periodically closed as shown.

In 2, I have shown another embodiment of my invention generally similar to that shown inFig. '1, but in which the contactor 8 .is held closed by a holding contact 22 thereon connected in circuit with the contactor energizing winding I I. In Fig. 2, the holding circuit for the coil H comprises the contact 22 connected in series circuit relation with a timing switch IS. The contacts of the switch i8 are normally closed and arranged to be opened periodically by the timing cam it. In all other respects, the embodiment of Fig. 2 is similar to that of Fig. 1 and like parts have been assigned the same reference numerals.

In operation of the arrangement shown in Fig. 2, the timing switch i2 is closed for a portion of each unit time interval defined by adjacent holes in the drum i and the timing switch it is opened for only an initial or included portion of the closure period of the timing switch 12. Thus, if in any given unit time interval the program switch 6 encounters a pin 3, an energizing circuit is completed for the winding H by the switch i2, and the holding circuit is simultaneously disabled by the switch I8 for a portion of the energizing interval. The switch 58, however, is closed before the switch i2 is opened, so that when the switch it is finally opened the holding circuit is eiiective. So long as the program switch 5 continues to encounter adjacent pins, this action is repeated during each closing interval of the switch so that the contactor 8 is maintained in its energized position. If, however, the prcgram switch 6 does not encounter a pin during any selected unit time interval, the timing switch i2 is ineffective to complete the contac'or energizing circuit, while the holding circuit is disabled for an interval by the timing switch it. Thus, the contactor 8 is dropped out and remains out until the program switch 53 encounters the next pin on the drum.

It will now be evident from the foregoing description of the operation of my invention that the timing switch i8 or E8" may be actuated to disable the holding or looking circuit at any time during the closure period of the timing switch :2, other than the final portion of the period. Thus, where in the appended claims the term initial portion is used with respect to the closure period of the switch [2, it shall be taken to mean a, portion which terminates prior to termination of the closure period, whether it begins at or after the beginning of the period.

While I have described only certain preferred embodiments of my invention by way of illustration, many modifications will occur to those skilled in the art and I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In combination, electromagnetic switching means, means for energizing said switching means comprising two pairs of normally open contacts in series circuit relation, first timing means for establishing a continuous series of unit time intervals, selectable program means arranged to close one of said pairs of cont cts for a predetermined portion of any of said unit time intervals, second timing means for recurrently cics'ing the other said pair of contacts for a predetermined period during each said unit interval, eriods being included in said predetermined portions of said unit intervals, holding includin a circuit independent of said energizing means for maintaining sald switching means in its energized position, andswitching means iii-said circuit actuated by said second timing means for recurrently disabling said holding means at least momentarily for an initial portion of each said predetermined period.

2. In combination, electromagnetic switching means, means for energizing said switching means comprising two pairs of normally open contacts in series circuit relation, first timing means for establishing a continuous series of unit time intervals, selectable program means arranged to close one of said pairs of contacts for a predetermined portion of any of said unit time intervals, second timing means for recurrently closing the other said pair of contacts for a predetermined period during each said unit interval, said periods being included in said predetermined portions of said unit intervals, latch means for maintaining said switching means in its energized position, and switching means including a circuit independent 01 said energizing circuit controlled by said second timing means for recurrently rendering said latch means ineffective at least momentarily for an initial portion of each said predetermined period.

3. In combination, electromagnetic switching means, means for energizing said switching means comprising two pairs of normally open contacts in series circuit relation, first timing means for establishing a continuous series of unit time intervals, selectable program means arranged to close one of said pairs of contacts for a predetermined portion of any of said unit time intervals, second timing means for recurrently closing the other said pair of contacts for a predetermined period during each said unit interval, said periods being included in said predetermined portions of said unit intervals, latch means for maintaining said switching means in its energized position, electromagnetic means including a coil for releasing said latch means, and means including a circuit independent 01' said first energizing circuit and a switch controlled by said second tim ng means for recurrently energizin said coil at l ast momentarily for an initial portion of each said predetermined period.

4. In combination, electromagnetic switching means. means for energizing said switching means comprising two pairs of normally open contacts in series circuit relation, first timing means for establishing a continuous series of unit time intervals, selectable program means arranged to close one of said airs of contacts for a predetermined portion of any of said unit time intervals, second timing means for recurrently closing the other said pair 01' contacts for a predetermined period during each said unit interval, said periods being included in said predetermined portions of said unit intervals, electromagnetic means including a holding circuit independent of said normally open contacts for maintaining said switching means in its energized position, and means including a cam switch periodically actuated by said second timing means for disabling said holding circuit at least momentarily for an initial portion of each said predetermined period.

5. In combination. a program control switch arranged to be recurrently opened and closed during a desired holding interval, switching means having an energizing circuit including said program switch, a normally open timing switch in series with said program switch, timing means for closing said timing switch for a predetermined portion of each closing interval of said program switch, holding means including a circuit independent of said energizing circuit for maintainipg said switching means in its energized position,

and switching means in said last named circuit controlled by said timing means for periodically disabling said holding means at least momentarily at recurrent instants falling within an initial portion of said predetermined portion of each said switch closing interval.

6. In combination, a program control switch arranged to be periodically opened and closed during a desired holding interval, switching means having an energizing circuit including said program switch, a normally open timing switch in series circuit relation in said energizing circuit, timing means for periodically closing said timing switch for a predetermined portion of each closing interval of said program switch, holding means including a circuit independent of said energizing circuit for maintaining said switching means in its energized position, and means including a second timing switch in said last named circuit controlled by said timing means for periodically disabling said holding means at least momentarily at recurrent instants falling within initial portion of said predetermined portion of each said switch closing interval.

'7. In combination, a program timing device arranged to define a continuous series of unit time intervals, a normally open program switch controlled by said device and arranged to be recurrently closed and opened within each said unit interval included in a desired holding period extending over consecutive unit intervals, electromagnetic switching means having an energizing circuit including said program switch, holding means including a circuit independent of said energizing circuit for maintaining said switching means in its energized position, and timing means including a switch in said last named circuit for periodically disabling said holding means at least once during each said unit interval and at an instant during closure but prior to opening of said program switch.

8. In a program control system, a continuously operable program timer defining a continuous series oi unit time intervals, means for selecting a series oi consecutive unit intervals constituting an uninterrupted holding period, a normally open program switch arranged to be closed by said timer and then reopened during each unit interval in a selected holding period, electromagnetic switching means having an energizing circuit controlled by said program switch, holding means including a circuit independent of said energizing circuit for retaining said switching means in a picked up position independently of said energizing circuit, and timing means including a switch in said last named circuit for periodically disabling said holding means at least momentarily during each said unit interval and at an instant during but prior to termination of closure of said program switch in each unit interval in which said program switch is closed.

CHARLES H. REX.

REFERENCES CITED The following references are of record in the file 01' this patent:

UNITED STATES PATENTS Number Name Date 2,157,858 Miller May 9, 1939 2,201,162 Elliott May 21, 1940 2,209,108 Briggs July 23, 1940 2,262,061 Somers Nov. 11, 1941 2,447,752 Hathaway Aug. 24, 1948 

